Field of Invention
The present invention relates to a method for improving the performance of a system that controls a intermediate lock position type continuously variable valve, and more particularly, to a method for improving the performance of a system that controls a intermediate lock position continuously variable valve by compensating an ignition timing without a drop in engine RPM due to CAM undershoot.
Description of Related Art
Recently, as the demand for improving fuel efficiency, low-speed torque, and output and reducing an exhaust gas increases, it has been required to improve the performance of a continuously variable valve timing system (or camshaft phaser system, hereafter, referred to as a CVVT) that optimally controls the timings of opening/closing intake/exhaust valves in accordance with the RPM of an engine.
As an example of satisfying the demand for improving the performance of a CVVT by improving response of a system and increasing the operation range of a cam, there is a intermediate lock position type continuously variable valve timing system (hereafter, referred as a intermediate lock position CVVT). In particular, in the intermediate lock position CVVT, a solenoid valve (for example, an OCV (Oil-Flow Control Valve)) that forms a channel by moving a spool (or plunger) is provided and an engine ECU (Electronic Control Unit) that applies PWM DUTY (Pulse Width Modulation Duty) controls the position, and the position of a cam is controlled not at the largest retarded (intake) position and the largest advanced position (exhaust), but the middle position (parking), so the response is improved and the use region of the cam is increased in comparison to the CVVT.
Therefore, according to the intermediate lock position CVVT, the effect of improving fuel efficiency by reducing a loss of pumping due to an increase of valve overlap of intake/exhaust valves is further increased, the effect of reducing an exhaust gas by re-burning a combustion gas due to internal EGR by optimizing the valve overlap according to engine conditions is further improved, and the effect of improving output and increasing low-speed torque by increasing volume efficiency by optimizing an intake valve timing according to engine conditions is further increased, thereby improving fuel efficiency and reducing an exhaust gas in comparison to a CVVT.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.